The work will proceed in the following directions: 1. Exploration of the function of the HiPIP type Fe-S cluster in the enzyme aconitase and the broader implications of our finding that the soluble mitochondrial HiPIP-type Fe-S protein is, in fact, the nonoxidative enzyme aconitase. 2. Studies on the mechanisms of electron transfer in the system: trimethylamine - trimethylamine dehydrogenase - acceptor flavoprotein as a model for electron transfer in systems involving Fe-S flavoproteins. 3. Attempts to purify particle bound alpha-glycerophosphate dehydrogenase from skeletal muscle to investigate whether it is a Fe-S protein and what the natural electron acceptor for this enzyme is. 4. Studies of transient, particularly activated intermediates of cytochrome c oxidase by multistep mixing techniques. 5. Further development of the rapid mixing freezing technique with particular emphasis on multistep mixing procedures and applications involving high viscosity liquids and high pressure.